US Secretary of State Hillary Rodham Clinton and North Korea exchanged pointed barbs Thursday, with Clinton declaring North Korea "has no friends left" and the communist regime calling the US secretary of state a "schoolgirl", reported the Associated Press.

The sharp words came as North Korea announced it had refused to re-enter talks to terminate its nuclear weapons program.

Clinton said the world has made it clear to Pyongyang that it has "no place to go," citing near unanimity among Asian nations, including China, on fully enforcing the latest UN sanctions against North Korea for its repeated nuclear and missile tests.

Warning the North's nuclear ambitions could spark an arms race in the region, Clinton said the US would continue to vigorously enforce tough U.N. sanctions and insist that the north "irreversibly denuclearise."

But she held out the prospect of restoring US diplomatic ties and other incentives - actions the Obama administration would be willing to consider if the North Koreans dismantle their nuclear program.

"We urge North Korea to return to the six-party talks, look beyond the past and join others in finding the way forward," said Thai Foreign Minister Kasit Piromya, who hosted the Asean Regional Forum, a security conference among 27 countries and organizations that ended Thursday.

Clinton, who trumpeted Washington's renewed involvement in Asia during the conference, departed the resort island for Washington, wrapping up a weeklong trip to India and Thailand.

"North Korea's continued pursuit of its nuclear ambitions is sure to elevate tensions on the Korean peninsula and could provoke an arms race in the region," Clinton told a news conference before her departure.

Just moments before she spoke, a spokesman for the North Korean delegation said his government would not return to talks with the US, Japan, South Korea, China and Russia, citing the "deep-rooted anti-North Korean policy" of the United States.

North Korea's Foreign Ministry, reacting to an earlier Clinton comment likening the regime to "small children" demanding attention, described her Thursday as "a funny lady" who sometimes "looks like a primary schoolgirl and sometimes a pensioner going shopping."

Clinton offered a somewhat more optimistic message about another trouble spot on the US foreign policy agenda: Myanmar, the military-run southeast Asian nation also known as Burma.

She praised Myanmar's government for committing to enforce the U.N. sanctions against North Korea, calling it important in light of Myanmar's suspected secret military links to North Korea. "There is a positive direction that we see with Burma," she said.

Clinton suggested Myanmar may have played a role this month in persuading a North Korean cargo ship suspected of carrying weaponry in violation of the sanctions to return home instead of continuing to its destination, which U.S. officials said was probably Myanmar.

Clinton also called on Myanmar to unconditionally release democracy leader Aung San Suu Kyi, who is accused of violating the terms of her house arrest and faces a five-year prison term.